On change of select "Template" I'd like to retrieve data from XML file and put in "Subject" textfield and "Body" textarea (sort of "pre-filling" them), based on the option of "Template" select

I.e, if I choose option with value="first", I'd like to fill "Subject" field with "My first subject" and "Body" textarea with "This is the first body". In the same way, if I choose option with value="second", I'd like to fill "Subject" field with "My second subject" and "Body" textarea with "This is the second body", and so on

Of course, if no selection is done, both "Subject" and "Body" fields should be empty...How to do this with jQuery and AJAX, please?